LiFePO4 battery

What it means

LiFePO4 — lithium iron phosphate — is a lithium battery chemistry widely used in marine installations. It stores less energy per kilogram than the chemistries used in cars, and it is chosen anyway, for reasons that matter more afloat than ashore.

Why boats use it

It is markedly more tolerant of abuse: it resists thermal runaway far better than the high-density alternatives, which on a vessel that cannot be walked away from is the decisive property. It also tolerates a great many charge cycles — commonly several thousand to eighty per cent of original capacity — and does not object to being left partly charged over winter. The penalty is weight and volume, which a hull can absorb more easily than a car can.

Why it matters

Chemistry sets the ceiling on how long the pack lasts and how it must be treated. Ask what the warranty covers, in cycles or years and to what remaining capacity, because on an electric boat the battery is the most expensive single component and the one that ages fastest.